Update Lambda examples to use node 20.x

[trivikr]

Is your feature request related to a problem? Please describe.

Source code uses deprecated Lambda nodejs16.x https://github.com/search?q=repo%3Aawslabs%2Faws-amplify-identity-broker%20nodejs16.x&type=code

• Deprecation was on Jun 12, 2024 and function create will be blocked on Feb 28, 2025

Lambda Supported Runtimes https://docs.aws.amazon.com/lambda/latest/dg/lambda-runtimes.html

Describe the solution you'd like

Update Lambda examples to use node 20.x, which was made available on Nov 15, 2023

Describe alternatives you've considered

N/A

[realtebo]

no info about how to do this in autonomy?